Selective Inhibition of Herpesvirus Deoxyribonucleic Acid Synthesis by Acycloguanosine, 2′-Fluoro-5-Iodo-Aracytosine, and ( E )-5-(2-Bromovinyl)-2′-Deoxyuridine

Abstract

The selectivity of inhibition of herpesvirus deoxyribonucleic acid synthesis by acycloguanosine, 2'-fluoro-5-iodo-aracytosine, and (E)-5-(2-bromovinyl)-2'-deoxyuridine was determined by isopycnic banding of 32P-labeled deoxyribonucleic acid from herpesvirus-infected and uninfected cells.An important property of an antiviral compound is the selectivity of its action. Most compounds with a high activity against herpesviruses are nucleoside analogs (3,8,9,11 press). To measure both viral and cellular DNA synthesis, nonconfluent cell cultures and a low multiplicity of infection were used. The selective action of acycloguanosine (ACG), 2'-fluoro-5-iodoaracytosine (FIAC), and (E)-5-(2-bromovinyl)-2'-deoxyuridine (BrVDU) on viral and cellular DNA synthesis in herpes simplex virus type 1 (HSV-1)-infected and uninfected Vero cells has been determined by isopycnic banding of DNA in CsCl gradients. These nucleosides have previously shown a high antiherpes activity (1,5,10,12,13) and are also known to require the presence of herpesvirus-induced thymidine kinase for their antiviral activity (2, 5, 10).ACG showed a high selectivity in the inhibition of viral DNA synthesis ( Fig. 1A to C; Table 1). When viral DNA synthesis was inhibited by 90% at 0.3 uM, only 15% inhibition of cellular DNA synthesis was observed. No effect on DNA synthesis in uninfected cells could be detected at this concentration and 310 ,M ACG was required for a 50% inhibition. The high selectivity found for ACG correlates well with earlier results showing that ACG is phosphorylated to a much higher extent to its mono-, di-, and triphosphate in HSV-1-infected celis than in uninfected cells and that ACG triphosphate is selectively accepted by HSV-1 DNA polymerase, leading to chain termination (5, 7).FIAC was less selective than ACG in the inhibition of viral DNA synthesis in infected cells ( Fig. 1D to F; Table 1). At 0.10 ,uM a 90% inhibition of viral DNA synthesis was obtained, whereas cellular DNA synthesis in infected cells was inhibited by 40%. However, DNA synthesis in uninfected cells was not inhibited at this concentration, and 64 ,LM FIAC was required to obtain a 50% inhibition, which confirms the results of Lopez et al. (10) showing a high selectivity by FIAC when effects on HSV-1 multiplication and cytotoxicity for uninfected Vero cells were compared.BrVDU inhibited viral DNA synthesis by 90% at a concentration of 0.6 uM ( Fig. 1G to I; Table 1). As in the case of FIAC, but not of ACG, the cellular DNA synthesis in infected cells was also affected, to 60%, at this concentration. In the uninfected cells, DNA synthesis was not affected by 0.6 juM BrVDU, and at 440 ,M a 50% inhibition was observed. These results agree with those of De Clercq et al. (1), who have shown previously that BrVDU inhibits HSV-1 multiplication at low concentrations, while not affecting the growth of uninfected cells.In a cell-free assay, BrVDU seems to be selectively phosphorylated by HSV-1 thymidine kinase (A. Larsson, unpublished data

The Multifunctional Deoxynucleoside Kinase of Insect Cells Is a Target for the Development of New Insecticides

“…Presumably, BVDU cannot efficiently reach the mitochondrial TK-2 to become converted to its phosphorylated derivative or, alternatively, BVDU is phosphorylated in the mitochondria by TK-2, but the phosphorylated product(s) are not harmful for this cellular compartment. These data are in agreement with observations published previously that BVDU very marginally inhibits growth of normal lung fibroblasts at 450 M (Machida et al, 1982), DNA synthesis of normal primary rabbit kidney cells or Vero cells at 300 M (De Clercq and Descamps, 1981;Larsson and Ö berg, 1981), the proliferation of bone marrow granulocyte-monocyte progenitor cells at 120 to 600 M (Wingard et al, 1983), and various lymphocyte responses at 150 to 300 M (Marmer et al, 1982;Wingard et al, 1983). In fact, BVDU has been used in the treatment of herpetic keratitis, herpetic gingivostomatitis, herpes labialis, herpetic encephalitis, and VZV infections (i.e., chickenpox, shingles) with immune-competent and immune-compromised patients.…”

Anti-herpesvirus activity of the acyclic nucleoside 9-(1,3-dihydroxy-2-propoxymethyl)guanine

“…The most proment compound in this area is acyclovir (17), a deoxyguanosine analog that inhibits herpesvirus replication at doses nontoxic to uninfected cells (15). The selectivity of the action of acyclovir is due to the fact that it is initially activated to acyclovir monophosphate by herpesvirus-specified thymidine kinase, but not to any great extent by cellular kinases (4,10).…”

9-(3,4-dihydroxybutyl)guanine, a new inhibitor of herpesvirus multiplication

“…A selective inhibition of HSV DNA synthesis in infected cells (Fig. 3) suggests that a phosphorylated form of DHBG selectively inhibits the viral DNA synthesis by analogy with inhibition by ACV (19) and foscarnet (18). It remains to be seen whether DHBG will act as a chain terminator.…”

“…Most of the HSV-1 and HSV-2 strains used have been described previously (13,15,28). The method used to determine viral and cellular DNA synthesis by 32p labeling and isodensity gradient centrifugation has been reported previously (18,19).…”